1. Field of the Invention
Endodontic instruments, more specifically: an instrument wherein the head and shaft are separately manufactured and then joined; wherein an instrument may have a shaft with a first composition and a head located at a removed end of the shaft, the head with a second composition; and an instrument with an integral retrieval means.
2. Background Information
Endodontic instruments are used to clean and shape a root canal, for subsequent filling. Prior art endodontic instruments are typically made from the same material and in a single step as an integral unit with an elongated working member having a cutting portion for cutting the canal and a non-cutting portion for insertion into a handle. A handle which is attached to the first or near end of the shaft is rotated while the instrument is inserted into the canal where the rotation of the cutting head or cutting portion against the walls of the tooth canal effects a reaming or cleaning of the canal.
Applicant provides a number of improvements in prior art endodontic instruments and irrigating devices. First, Applicant provides an endodontic instrument with a working portion created by the joiner of a separate shaft (non-cutting portion) and a separate head (cutting portion). This is provided in place of the prior art teaching of a unitary working member with a cutting portion at one end thereof. Applicant""s endodontic instrument provides for a number of advantages over the prior art as set forth more fully below.
Further Applicant provides an endodontic instrument including means for retaining a shaft on the instrument if the shaft were to break.
Further, Applicant provides an endodontic instrument with a friction grip handle for engagement with a drive tool.
Further, Applicant provides for a unique device, for injecting and agitating irrigation fluid into the root canal system.
The purpose of the shaft is to locate the head of the instrument into the canal and bring it back. Further, the shaft is used to drive the head. In the past, materials of the one piece head and shaft were the same (typically metal) so you could not optimize head and shaft requirements. While the shaft should be flexible to keep the head centered in the canal and be capable of bringing the head into and out of the canal, the head of the shaft should be an effective cutting agent shaped and made of a material that will promptly and effectively cut the canal walls.
Applicant provides for an endodontic instrument in which a shaft and head are manufactured separately, then joined together, with typically, a handle attached to the shaft on the end opposite the head. The shaft and the head may be manufactured from the same material or from different material.
In the past, the shaft and head were an integral member made of the same composition; that is, stainless steel, nickel titanium, etc. Applicant also provides a novel device with two or more different materials; a shaft of a first composition (optimally flexible and durable) and the head of a second composition (optimally hard and shaped with cutting edges) for effectively cutting tooth canal material.
The function of the head is to cut, clean, and stay centered in the canal and remove the abraded material. This is best performed by materials whose properties are different than the function of the shaft, which should be flexible, durable, and capable of placing a head into and out of a root canal.
Breakage of an instrument in a canal creates obvious problems. Prior art methods for avoiding such problems are, in the main, preventative, including keeping a close track of the number of times that the instrument has been used so its use may be discontinued after a number of uses. Therefore, it is clear that an instrument that is capable of being retrieved if broken would provide a greater utility to the dentist.
Rotary endodontic instruments typically rotate rapidly and flex while the dentist is shaping and cleaning within the root canal. The repeated flexing causes them to, ultimately, fail by breaking, usually along the shaft between the handle and the head of the instrument. If the breakage occurs during use, the dentist is faced with the often formidable task of recovering the broken pieces or leaving the broken pieces in the tooth.
Applicant provides a solution to the breakage problem by focusing on the retrieval of the broken pieces of the instrument. By providing structural means to retrieve the broken pieces from the tooth, Applicant""s endodontic instrument may be made or constructed with a shaft of stainless steel, nickel-titanium or any other suitable material. The breakage of a shaft becomes less of a concern to the dental professional when structural means are provided that will provide a retrieval mechanism.
When breakage of the instrument occurs inside the tooth the broken pieces of the instrument should be removed. An invention which has a built-in retrieval device clearly has advantages in such a situation. Applicant provides in the following description and claims a design for such an instrument.
It is an object of the present invention to provide an endodontic instrument which optimizes advantageous properties of a head made of a first composition and optimizes advantageous properties of a shaft made of a second composition.
It is another object of the present invention to provide an endodontic instrument, such as a drill with a built-in, broken tool retrieval device.
This and other objects are provided for in an invention set forth below and described with reference to the attached figures.
Applicant also provides yet another unique endodontic instrument for cleaning a tooth canal and a method for manufacturing the same. This instrument includes a separate shaft to which a separate head is joined. Applicant""s novelty lies in providing for manufacturing the shaft separate and apart from the head and, following the manufacturing the head and shaft separately then joining the two. This provides for advantages including optimizing the performance of the two individual components. It is noted in this embodiment of this applicant""s invention that the separate manufacturing steps of manufacturing the shaft and the head may be provided wherein the shaft and head material are of the same composition or wherein the shaft and head material are different compositions.
In the first instance, for example, the shaft and head may be made from stainless steel, nickel titanium, plastic or the like. The shaft is manufactured and fashioned as an elongated typically cylindrical, hollow tube or solid wire, coil wound section, or a series of gears, or wire mesh with the head manufactured separately in a manner and shaped for efficient cutting and cleaning. The pieces are then joined as by bonding, welding, gluing, etc. (method of joining).
On the other hand, a shaft may be made as set forth above and a head may be provided of a different material as such as those materials set forth above and then the shaft and the head joined. It is noted that the separate manufacturing steps of manufacturing the two pieces (shaft and head) apart from one another allows the instrument designer greater variation in the dimensions and shape of the individual piece then the prior art method which shapes the shaft and the head as an integral piece in the single manufacturing process. That is, in the prior art a blank was provided from which an integral head and shaft unit is tooled.
Applicant""s provide for this and other objects by providing a rotatable endodontic instrument having a handle for attachment to a shaft, the shaft with a near end and a removed end, the handle at the near end thereof and a head, cooperating with the shaft at the removed end of shaft so as to rotate therewith. Applicant further provides for a sleeve, dimensioned for receipt over the shaft, to substantially enclose the shaft between the handle and the head of the shaft, with the sleeve and the shaft being glued, soldered or otherwise attached to one another. Therefore, if breakage of the shaft occurs the sleeve still maintains its integrity and will substantially enclose the broken piece, typically preventing it from escape from the instrument and remaining in the canal.
Applicant further provides for this and other objects and purposes in providing an endodontic instrument which includes a shaft, the shaft enclosed by a coil spring and attached to the coil spring such that both the shaft and the coil spring rotate together. At one end of the shaft is a head and at the other end of the shaft is a handle. Rapid rotation by the handle allows the head to do its cutting work on the tooth. However, should the shaft break the coil spring will retain, within the coil, the broken piece.